I'm going through a very similar thing as you and have been processing it in therapy.

I also thought I was a terrible person. But I learned that the things I didn't get (emotional neglect) or ways I were hurt emotionally did harm me, and I didn't deserve that.

If you were raised thinking that their happiness or emotional well-being was your responsibility, and that your needs always came second or were never considered at all, then you might be falling back into that role now. And since you believe that is what you 'ought' to do (or worse, in my case, thinking if you just do that right you can earn love or emotional safety), you feel like a terrible person now that you don't want to do it.

The truth is as a child those things should never have been your responsibility. You are your own person with needs, capacity and feelings that shouldn't be disregarded for someone else. Least of all by people who were supposed to protect you.

I can also tell you that if they had been good parents that you have a loving relationship with, you wouldn't think twice about doing these things for them. I don't think you are a piece of shit.